**Acknowledgement**

The authors thank Professors S. E. Donnelly, Drs. N. M. Boag, S. Simpson (Manchester, U.K.) for very critical discussions on electron microscopy, X-ray diffraction and chirality, and for using the High Resolution Electron Microscope (Joel T 3010) and the X-ray diffraction equipments. Professor K. Stadtlander (Iserlohn, Germany) for lending us the Olympus light microscope and the video camera. Financial support from the Biomaterials Project (Bruxelles, Grant BMH4-CT-96-0013), Chemical-Biotechnological Laboratories Inc (Iserlohn) and from Orthomol (Langenfeld, Germany) are gratefully acknowledged.
